Particle sorting method and apparatus

ABSTRACT

A particle sorting method and apparatus for separating minute particles incorporated in a liquid stream in accordance with selected particle parameters. Particles such as biological cells to be separated are incorporated in the inner or central portion of a confined coaxial flow stream which includes an outer cellfree fluid sheath portion. This coaxial flow stream is released through a vibrating nozzle for inspection by one or more cell sensing means for sensing cells in the jet stream immediately downstream of the nozzle. Beam illumination and/or observation of the jet stream for particle sensing is effected outside of the nozzle. Vibration of the nozzle breaks the coaxial jet stream into a series of uniform drops downstream of the cell sensing means, and signals from said means are used to initiate delayed charging pulses applied to preselected cell-containing drops as they break from the vibrating fluid jet. Nozzle vibration is synchronized with the charging pulse to prevent separation of drops from the stream during the drop charging pulse on and off transition times, thereby preventing undesired drop charging. The drops pass between charged deflection plates where the charged drops are deflected into appropriate receptacles. By using a plurality of sensing means such that all cells are sensed by one sensor, and only certain cells, i.e. cells characterized by a particular parameter value, are sensed by another sensor, drops containing both cells characterized by a particular parameter and cells not characterized by that parameter can be sorted away from the receptacle for cells characterized by that particular parameter.



1. A method of separating certain particles from others contained in a fluid stream comprising, producing a coaxial flow stream having an inner stream portion of particle containing fluid and an outer stream portion of sheath fluid, jetting the coaxial flow fluid stream, modulating the jet stream velocity in the direction of the stream axis to break the stream into discrete drops, detecting certain particles in the inner stream portion of the coaxial flow stream, charging the jet stream while drops containing detected particles break from the jet stream to supply such drops with an electrical charge, synchronizing the charging with the modulating of the jet stream to ensure against parallel drop charging during on and off transitions of the drop charging pulse, and deflecting the charged drops in an amount related to the drop charge.
 2. The method of particle separation as defined in claim 1 wherein the coaxial flow stream is jetted into the atmosphere, and including detecting directly through the atmosphere desired particles in the inner stream portion of the jet stream as said stream travels through the atmosphere.
 3. The method of particle separation as defined in claim 1 wherein said certain particles detected are those characterized by a particular parameter value, the method also including detecting other particles in the inner stream portion of the coaxial flow stream which are characterized by other parameter values, charging the jet stream by use of different drop charging pulse while drops containing detected particles characterized by other parameter values break from the stream to supply such drops with a different drop charge, and modifying charging of the jet stream while drops containing both particles characterized by a particular parameter and those characterized by other parameters break from the stream for a different deflection of such drops.
 4. A method of separating certain particles from others contained in a jet stream comprising, modulating the jet stream velocity in the direction of the stream axis to break the stream into discrete drops, detecting certain particles in the jet stream, charging drops containing detected particles during a drop charging pulse period, synchronizing the drop charging pulse period with the modulating of the jet stream to prevent drops breaking from the stream during drop charging on and off transitions, and deflecting charged drops in an amount related to the drop charge thereon.
 5. The method of particle separation as defined in claim 4 wherein said jet stream travels through the atmosphere, and including detecting directly through the atmosphere particles in the jet stream as said stream travels through the atmosphere.
 6. The method of particle separation as defined in claim 4 including detecting other particles in the jet stream in addition to detecting said certain particles therein, charging the jet stream by use of a different drop charging pulse while drops containing other detected particles break from the stream to supply such drops with a different drop charge, and modifying charging of the jet stream while drops containing both detected certain and other particles break from the stream for a different deflection of such drops.
 7. A method of separating certain particles from others contained in a stream which is jetted from a nozzle into the atmosphere comprising, modulating the jet stream to break the stream into discrete drops at a distance from the nozzle, detecting directly through the atmosphere certain particles in the jet stream while the stream travels through the atmosphere before the stream into discrete drops, charging drops containing detected certain particles, and deflecting charged drops in accordance with the drop charged thereon.
 8. The method of separating particles as defined in claim 7 including synchronizing the charging of drops with the modulating of the jet stream.
 9. The method of separating particles as defined in claim 7 including, detecting other particles in the jet stream, charging drops containing detected other particles to another drop charge, and modifying charging of drops containing both certain and other detected particles.
 10. A method of separating certain particles from others contained in a jet stream comprising, modulating the jet stream to break the same into discrete drops, detecting certain particles in the jet stream, detecting other particles in the jet stream, providing drops containing detected certain particles with a first drop charge, those containing detected other particles with a second drop charge, and those containing both detected certain and other particles with a third drop charge, and separating drops according to their drop charge.
 11. The method of particle separation as defined in claim 10 wherein the jet stream travels through the atmosphere before breaking into discrete drops, and including employing first and second particle detecting means to detect said certain particles and said other particles directly through the atmosphere as the stream travels through the atmosphere before breaking into discrete drops.
 12. The method of particle separation as defined in claim 10 including synchronizing the drop charging with the modulating of the jet means to assure against partial drop charging.
 13. Apparatus for separating particles contained in a fluid comprising, means including a nozzle assembly for producing a stream of particle containing fluid, means for jetting the stream from the nozzle assembly, means for modulating the velocity of the stream to break the jet stream into discrete drops, detector means for detecting particles in the stream, pulse charging means responsive to the detector means for charging selected drops, means for synchronizing the pulse charging means and modulating means to ensure against partial drop charging during on and off transitions of the pulse charging means, and means for deflecting charged drops an amount related to the drop charge.
 14. The apparatus as defined in claim 13 wherein the stream is jetted into the atmosphere, and the detector means are positioned outside the jetting means where the jet stream travels through the atmosphere.
 15. The apparatus as defined in claim 13 wherein particles characterized by a particular parameter are detected by said detector means, said apparatus including second detector means for detecting substantially all particles in the stream, including particles characterized by said particular parameter and those not so characterized, said pulse charging means being responsive to both said detector and second detector means for charging drops containing particles characterized by said particular parameter to a drop charge of one value, for charging drops containing particles not characterized by said particular parameter to another value, and for modifying the drop charge for drops containing both particles characterized by said parameter and those not so characterized.
 16. The apparatus as defined in claim 13 wherein a coaxial flow stream having an inner stream portion of particle containing fluid and an outer portion of sheath fluid is produced by said stream producing means, which coaxial flow stream is jetted into the atmosphere by said jetting means.
 17. A method of separating certain particles from others contained in a fluid stream comprising, jetting the fluid stream, detecting certain particles in the fluid stream, modulating the fluid stream velocity in the direction of the stream axis to break the stream into discrete drops, charging drops containing detected particles during drop charging pulse periods, synchronizing the drop charging pulse period with the modulating of the fluid stream to prevent drops breaking from the stream during drop charging on and off transitions, and deflecting charged drops in an amount related to the drop charge thereon.
 18. The method of particle separation defined in claim 17 wherein said fluid stream comprises a coaxial flow stream having an inner stream portion of particle containing fluid and an outer stream portion of sheath fluid.
 19. The method of particle separation defined in claim 17 wherein the fluid stream is jetted into the atmosphere, and wherein the step of detecting certain particles in the fluid stream is effected at a point along the jet stream travel through the atmosphere before the stream breaks into discrete drops.
 20. The method of particle separation defined in claim 17 wherein said certain particles detected are those characterized by a particular parameter value, the method also including, detecting other particles in the fluid stream which are characterized by other parameter values, charging the jet stream by use of a different drop charging pulse while drops containing detected particles characterized by other parameter values break from the stream to supply such drops with a different drop charge, and modifying charging of the jet stream while drops containing both particles characterized by a particular parameter and those characterized by other parameters break from the stream for a different deflection of such drops. 